During human evolution, our cerebral cortex increased in size in response to new environmental challenges. The cerebral cortex is the site of diverse processes, including visual perception and language acquisition. However, no accepted unitary theory of cortical function exists yet. One hypothesis is that there is an evolutionarily conserved neural circuit that implements a simple and flexible computation. This idea is known as the “canonical circuit.” As Gary Marcus, Adam Marblestone, and Thomas Dean note in a perspective piece in Science, there is still no consensus about whether such a canonical circuit exists nearly four decades later. Researchers argue that there is little evidence that such a uniform structure can capture the diversity of cortical function in simple mammals.